The need for maintaining clear visibility through viewing windows has long been recognized, particularly in the shipping industry, the tooling and machining industry, the land vehicle industry and in many other areas where clear visibility through a window is required.
Visibility through a viewing window is commonly impeded when, for example, water and other debris impact the window. In the machining and tooling industry, there is a need to maintain the window through which the work piece is viewed clear of liquid machining lubricant, metal chips, and debris generated during the machining process. However, the windows tend to impede, rather than improve, visibility because the chips scratch the window. Furthermore, the lubricants or other liquids obscure visibility through the window because of their formulation to increase the "wetting" action, which results in substantially coating the window.
In the and shipping and land vehicle industries, reciprocating wipers have been used to remove water and debris from windows, such as windshields. Windshield wipers do not reciprocate fast enough to maintain a clear view through the window, particularly a ship's window, so as to overcome the problem of water collecting on the window.
Rotating windows have been used to overcome some of the above-noted problems, particularly in the machining and shipping industries. A rotating window places a centrifugal force on any object that comes into contact with the window and slings the object immediately off the rotating window.
Conventional rotating windows are driven by electric motors. Electrically driven rotating windows suffer from several drawbacks. In the high moisture environments in which rotating windows are typically used, components such as motor poles may corrode, causing the motor to fail and requiring that the motor be replaced. If the motor fails while in use, the motor or the entire rotating window must be replaced. If the rotating window is on a machining assembly, the machine assembly typically is taken out of service for a period of time until replacement is completed.
Air-driven windows have been used to overcome some of the above-mentioned problems. Existing air-driven windows are driven in the manner of an anemometer by directing air toward shallow cups or other features that catch the air to spin the window. Existing air-driven windows, however, have several shortcomings. One problem is that air passing into and out of the shallow grooves creates substantial noise, which may interfere with a user's ability to concentrate on the task at hand, such as piloting a vehicle or completing a machining operation.
A further problem with conventional air-driven windows is that they are not efficient. Air may reflect from various surfaces of the grooves so as to impede the flow of air entering and exiting the grooves, reducing the overall propulsive force of the air on the rotating window. Once the air has passed out of the grooves, the air remains trapped in the region between the rotating window and a stationary window to which the rotating window is attached. The trapped air creates friction with the rotating window, reducing the rotational speed and effectiveness of the window.